Method of preparing an elastomer



Patented Jan. 4, 1949 QLUN D STATES O C Iral B. Johns, Ames, Iowa, assigner" tolowa State College Research Foundation, Anne's; Iowa, a

corporation of Iowa No Drawing. Original application December 1 1,

1942, Serial No. 468,691. .Divided and this -application September 12, l li l g serialNo. 615,321

This invention relates to an elastomer and a method of preparing the same, and more particularly to a polymerized material forming a synthetic rubber and possessing characteristics similar to those of natural rubber.

In accordance with the present invention, an elastomer or synthetic rubber is easily andreadily prepared from furfural, which in turn is obtained by digesting agricultural waste materials with acid. With this process, the natural product is readily converted by successive steps of treatment to synthetic rubber.

The invention contemplates the hydrogenation of furfural to reduce the aldehyde radical thereof, and also to saturate the unsaturated double .bonds of the furfural, and the subsequent dehydration of the product to form piperylene. The piperylene is then polymerized to form the elastomer or synthetic rubber.

The broad steps of the invention include the tained in commerce by the acid digestion of oat hulls and is a liquid boiling at approximately 160 G. Since furfural can be produced from a great many Waste agricultural materials, including oat hulls, the source is almost unlimited.

In the first step of the reaction, furfural in the vapor phase is mixed with an excess of hydrogen at a temperature above the'boiling point of furfural, the temperature preferably being in the neighborhood of 200 (L-225 C. Thereaction is carried out in the presence of a suitable catalyst, such as finely-divided metallic copper which has been reduced from cupric hydroxide on a charcoal bed or on a copper screen support. Preferably, the reaction is carried out by passing hydrogen through a bath of liquid furfural, so that the furfural will be entrained by the hydrogen, and passing the vapor phase mixture of furfural and hydrogen through a suitable furnace containing the catalyst, the furnace being maintained at the desired temperature. Since a large Claims. (01. zco a si excess of hydrogenispreferably used, the excess hydrogen may berecirculated and again passed through the fu'rfuralbath and the reaction furnace. In the operationbf this step, it has been foundthat approximately three times as much hydrogen is" passed through the furnaceas is reactedwith the furfural.

Although, any suitable catalyst may be used forlthe' reaction, a catalyst consisting of finelydivided metallic copper .on .a charcoal bed has been foundto' be partioularly desirable. This catalystm'ay beprepared by chemically precipitating cupric'hydroxide on charcoal and. then heating the charcoal in an atmosphere of hydrogen to a temperature of approximately 210 C. to reduce thecupric hydroxide to metallic copper. The resulting producuincluding the charcoal catalyst bed,,may be placed in the furnace where it Will act as a catalyst forthe reaction.

. The reaction between. the. furfural and hydro-.

genresults inia product consisting predominantly of ,fsylvan. In this product, the aldehyde radical of the furfural has been reduced to a methyl radical. 'Ihe sylvan. may be obtained by passing the gaseous product from the reaction furnace throughasuitable condensing bath. When the product is condensed, it will be found to separate into two layers, in which the water formed in the reaction,andunreactedfurfural provide the lower layer, while, the sylvan is found in the upper layer. The sylvan may be separated by any suitable method, such, f,or example, as distillation. In the reaction, it,. i s theoretically possible to obtain furfuryl alcohol, but under the reaction conditions set forth the .amount of furfuryl alcohol produced isverysmall. l y

The product of the first step of the reaction, which consists predominantly of sylvan, is then subjected to; further catalytic hydrogenation. In

this step. of the reaction, the sylvan is mixed in the vapor; phaseawith an excess of hydrogen at. anelevated temperature in the, presence of a suitable catalyst, such, for example, as a partially? activated nickel catalyst. The sylvan may be mixedpwith, the hydrogen by passing the gaseous hydrogen. througha-liquid bath of the sylvan to entrainuthe sylvan,v and themixture may then be passed throughareaction furnace which may.

be. maintainedat a temperature of 112 C.-135 C.

and is preferably maintained ata temperature of" 115 C.- C. The excess hydrogen is recirculated for the reaction.

A suitable catalyst for this step of the reaction may be prepared by subjecting a powdered nickel-aluminum alloy, of the type known as Raney nickel, to a partial activation with an alkali, such as sodium hydroxide. The nickelaluminum alloy may be placed in a dilute solution of sodium hydroxide in which there is only sufiicient sodium hydroxide present to dissolve a portion of the aluminum. For example, 40 gms. of the nickel-aluminum alloy may be placed in a solution containing approximately gms. of sodium hydroxide. The partial activation of the catalyst is important in this step of the reaction since if the catalyst is subjected to treatment with a concentrated solution of sodium hydroxide, the reaction will produce a decomposition of the sylvan and result in the formation of methane which, when mixed with hydrogen, will prevent any further reaction.

It may be possible to use other catalysts for the hydrogenation of the sylvan. For example, a catalyst consistin of powered nickel prepared by the reduction of nickel oxide precipitated on charcoal by ammonium carbonate, may be used. Nevertheless, the partially-activated Raney nick.- el catalyst has been found to be particularly suitable for this process.

In the next step of the reaction, the tetrahydrosylvan or the hydrogenated product is subjected to catalytic dehydration to form a product having a conjugated double bond system. This product is formed by heating the tetrahydrosylvan in the presence of a dehydrating catalyst, such as a phosphate salt having Weakly acid reaction. A suitable catalyst for this purpose is mercuric phosphate precipitated on a bed of granular aluminum oxide. The reaction is preferably carried out at a temperature in the neighborhood of 325 C. An inert gas, such as nitrogen, may be passed through a bath of liquid tetrahydrosylvan, and by entrainment will carry the tetrahydrosylvan through the reaction, chamber which may be heated to the desired temperature. The catalyst is placed in the reaction chamber, and the tetrahydrosylvan is converted topipery lene, which is also known as l-methyl butadiene or as 1,3-pentadiene. At the same time a .oertain amount of 1,4-pentadiene is produced. This substance, having a boiling point of 0., can be separated from 1,3-pentadiene boilingat 42 C. by fractional distillation. The amount of 1,4-pentadiene formed compared to the amount of 1,3-pentadiene formed in a given reaction'hasbeen found to' depend somewhat on the conditions of the reaction.

A suitable catalyst for this reaction may be prepared by reacting mercuric chloride with trisodium phosphate in an aqueous solution to precipitate mercuric phosphate. Preferably, the precipitate is collected on a bed of granular activated aluminum oxide.

The piperylene may be polymerized in the presence of any suitable catalyst to form an elastomer. For example, the piperylene, which is a liquid boiling at 42 C., may be emulsified in 'an aqueous solution of an emulsifying agent of mildly alkaline reaction, such as sodium or am-' monium oleate alone or with styrene or acryloni trile or any suitable substance as a copolymer. A

suitable peroxide may be used as a catalyst in the reaction. For example, such a catalyst as emulsion is obtained. Dilute acetic acid causes coagulation of the emulsion. The soft mass, after washing, possesses characteristics similar to those of natural rubber. It possesses elastic properties and softens on heating and stiffens on cooling. It can be successfully vulcanized to form a'trulyrubber-like substance. The piperylene, in the liquid state, has also been polymerized directly by means of anhydrous aluminum chloride.

.:The present application constitutes a division of my copending application, Serial Number 468,691, filed December 11, 1942, for Elastomer ment of the invention, it will be apparent that this is for the purpose of illustration only and changes and modifications may be made without departing from the spirit and scope of themvention.

I claim:

1. A process for the production of sylvan which comprises the passing of hydrogen through a bath of liquid furfural to substantially saturate the hydrogen with furfural and the passage of the furfural-laden hydrogen at a temperature above 160 Cover a reduced copper hydroxide catalyst reduced at a temperature of about 210 C.

2. A process for the production of Sylvan which comprises the passage of furfural-laden hydrogen at a temperature above 160 C. over a reduced copper hydroxide catalyst deposited upon a carrier, said copper hydroxide being reduced at a temperature of about 210 C.

3. A process for theproduction of sylvan which comprises the passage of furfural-laden hydrogen at a temperature of 160 C. over a reduced op er. hydroxide catalyst deposited upon charcoal, said copper hydroxide being reduced at a temperature of about 210 C.

4. A'process for the production of sylvan which comprises the passing of hydrogen through a bath of liquid furfural to substantially saturate the hydrogen with furfural and the passage of the furfural-laden hydrogen at a temperature of 200"to 225 C. over a reduced copper hydroxide catalyst, the copper hydroxide being reduced at a temperatureof about 210 C.

5. A process for the production of sylvan which comprises the passage of furfural-laden hydrogen at a temperature of 200 to 225 C. over a reduced copper hydroxide catalyst deposited upon a carrier, the copper hydroxide being reduced at a temperature of about 210 C.

IRAL B. JOHNS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,400,247 Stefi'ens Dec. 13, 1921 1,739,919. Ricard et al Dec. 17, 1929 2,034,077 Arnold Mar. 17, 1936 2,077,422 Lazier Apr. 20', 1937 2,120,958 Coons June'14, 1938 Guinot Feb. 17, 1942 Certificate of Correction Patent N 0. 2,458,001. January 4, .1949. IRAL B. JOHNS It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 3, line 19, for the word powered read powdered;

and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 3rd day of May, A. D. 1949.

THOMAS F. MURPHY,

Assistant Gonvmissz'oner of Patents. 

